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42 (number)

In mathematics

Forty-two is a composite number; its factorization 2 · 3 · 7 makes it the second sphenic number and also the second of the form { 2 · 3 · r }. As with all sphenic numbers of this form the aliquot sum is abundant by 12. 42 is also the second sphenic number to be bracketed by twin primes; 30 also rests between two primes. 42 has a 14 member aliquot sequence 42, 54, 66, 78, 90, 144, 259, 45, 33, 15, 9, 4, 3, 1, 0 and is itself part of the aliquot sequence commencing with the first sphenic number 30. Further, 42 is the 10th member of the 3-aliquot tree.

It is a Catalan number. Consequently 42 is the number of non-crossing partitions of a set of five elements; the number of triangulations of a heptagon; the number of rooted ordered binary trees with six leaves; the number of ways in which five pairs of nested parentheses can be arranged; etc.

The eight digits of pi beginning from 242,422 places after the decimal point are 42424242.

Given 27 same-size cubes whose nominal values progress from 1 to 27, a 3×3×3 "magic cube" can be constructed such that every row, column and corridor, and every diagonal passing through the center, comprises 3 cubes whose sum of values is 42.

In science

In 1965, mathematician Paul Cooper theorized that the fastest, most efficient way to travel across continents would be to bore a straight hollow tube directly through the earth, evacuate it (remove the air), and then just fall through. The first half of the journey consists of free-fall acceleration, while the second half consists of an exactly equal deceleration. The time for such a journey works out to be 42 minutes. Remarkably, even if the tube does not pass through the exact center of the earth, the time for a journey powered entirely by gravity always works out to be 42 minutes, as long as the tube remains friction-free. (The same idea was proposed by Lewis Carroll in Sylvie and Bruno, volume 2, chapter 7, without calculation).

In astronomy

In January 2005, Asteroid 2001 DA42 was given the name Asteroid Douglasadams, named for the author Douglas Adams who popularized the number 42 and died in 2001. With even his initials in the provisional designation, Brian G. Marsden, the director of the Minor Planet Center and the secretary for the naming committee, said, "This was sort of made for him, wasn't it?"

42 also occurs in other religions. There are 42 principles of Ma'at, the Ancient Egyptian personification of physical and moral law, order, and truth. In the judgement scene described in the Egyptian and the Book of the Coming/Going Forth by Day (the Book of the Dead (which evolved from the Coffin Texts and the Pyramid Texts)), there are 42 Gods and Goddesses of Egypt, personifying the principles of Ma'at, who ask questions of the departed, while Thoth records the answers, and the deceased's heart is weighed against the feather of Truth (Ma'at). These 42 correspond to the 42 Nomes (Governmental Units) of Egypt. If the departed successfully answers all 42, s/he becomes an Osiris.

In Judaism, the number (in the Babylonian Talmud, compiled 375 AD to 499 AD) of the "Forty-Two Lettered Name" ascribed to God. Rab (or Rabhs), a 3rd century source in the Talmud stated "The Forty-Two Lettered Name is entrusted only to him who is pious, meek, middle-aged, free from bad temper, sober, and not insistent on his rights". [Source: Talmud Kidduschin 71a, Translated by Rabbi Dr. I. Epstein]. Maimonides felt that the original Talmudic Forty-Two Lettered Name was perhaps composed of several combined divine names [Maimonides "Moreh"]. The apparently unpronouncable Tetragrammaton provides the backdrop from the Twelve-Lettered Name and the Forty-Two Lettered Name of the Talmud.

42 is the number with which God creates the Universe in Kabalistic tradition. In Kabbalah, the most significant name is that of the En Sof (also known as "Ein Sof", "Infinite" or "Endless"), who is above the Sefirot (sometimes spelled "Sephirot"). The Forty-Two-Lettered Name contains four combined names which are spelled in Hebrew letters (spelled in letters = 42 letters), which is the name of Azilut (or "Atziluth" "Animation"). While there are obvious links between the Forty-Two Lettered Name of the Babylonian Talmud (see further up this page) and the Kabbalah's Forty-Two Lettered Name, they are probably not identical due to the Kabbalah's emphasis on numbers. The Kabbalah also contains a Forty-Five Lettered Name and a Seventy-Two Lettered Name.

Since Adams's book, people have looked for and found 42 in older literature, such as Shakespeare's plays and Carroll'sAlice, which has 42 illustrations. In Chapter XII, the king explains "the oldest rule in the book": "Rule Forty-two. All persons more than a mile high to leave the court". Carroll also uses the number in a line in The Hunting of the Snark : "He had forty-two boxes, all carefully packed..."

42 goes back all the way to the very beginning of literature. The first book to be printed with movable type, the famous Gutenberg Bible, is also known as the '42-line Bible', after the number of lines of print on each page.

In The Property of a Lady from Octopussy (the earlier editions of the three-part short story book included this story), had James Bond (a character created by Ian Fleming) attending an auction to identify a top KGB spy. This spy was to raise the value of a Faberge Egg so that his female double agent working in MI5 (The British Secret Service) would get more money (as a way to monetarily pay her back for many years of service) from the sale of her (previously sent from Russia) Faberge Egg. The lot number of the Faberge Egg was 42.

In Batman Begins, the number 42 appears on the mud flaps of the lorry containing drugs for Carmine Falcone. 42 also appears in The Dark Knight on the timer of the bomb that the Joker has set up for Harvey Dent and Rachel Dawes.

In The Fugitive starring Harrison Ford, the prison bus at the start of the film had the number 42 written on the side.

In video games

In the popular PC game, Spore, reaching the center of the galaxy yields a powerful item known as the "Staff of Life" which has a limited 42 uses. It also grants the player an achievement titled "42". These are both a direct reference to The Hitchhiker's Guide to the Galaxy.

The application icon for PCalc for iPhone, the mobile version of the popular calculator app, is a calculator screen displaying the number 42. (The icon for the desktop version displays an equation which works out to 42.)

In other fields

In Japanese, 4 (shi) and 2 (ni) are together pronounced like "going to death" (死に). Because of that, in Japan, 42 is considered as a disastrous number. This happens in Hong Kong too, as 42 sounds like "easy death" in Cantonese.